The ability of insulin to enhance the incorporation of label from bicarbonate into protein and into TCA-soluble metabolites in rat adipose tissue will be carefully investigated. The influence of a variety of substances, such as epinephrine, energy substrates, insulin-like agents, verapamil and cyclic-nucleotides on this action of insulin will be explored. Mitochondria will be isolated from hormone-treated tissue and examined for a persisting change in Co2 fixation. Experiments designed to establish the precise step altered by insulin, i.e., pyruvate transport into mitochondria or pyruvate carboxylase will be performed. The effects of insulin on bicarbonate incorporation into protein will be compared with the effects on tritiated water incorporation to establish the magnitude of the action of insulin on protein synthesis. The goal of the work is to describe in detail a previously unrecognized action of insulin and look into the mechanism of the effect. Ultimately it is planned to use the effect in attempts to identify the second messenger of insulin's action on adipose tissue mitochondria.